1. Field of the Invention
This invention is related to a method of controlling excessive electroforming portion of an oscillating plate and in particular to one which applies direct current and alternating current electroforming process to eliminate excessive electroforming portion on the projection of the oscillating plate.
2. Description of the Prior Art
Ink-jet printers generally fall into two categories, i.e. the bubble type ink-jet printers and piezoelectric ink-jet printers. However, what the manufacture concerns most for piezoelectric ink-jet printers is related to the oscillating plate beside the ink cabin.
The working principle of ejecting ink from the piezoelectric print head will now be described hereinafter. Referring to FIG. 1, ink is first filled into the ink cabin 15 and then a ceramic piezoelectric actuator 12 is used for pushing the projection 14 on the oscillating plate 13 to squeeze ink out of the ink cabin 15 through nozzles 11. The print head generally includes a plurality of nozzles. The number of nozzles depends on the resolution of the printer. That is, if the printer has a higher resolution, its print head will have more nozzles.
Referring to FIG. 2, the oscillating plate 13 and the projection 14 are made of nickel by electroforming. A thin layer is first made by electroforming for 4 minutes to be used as the oscillating plate 13. Then, the area 19 is coated with a light interrupting agent for preventing current from flowing therethrough. Finally, the area 18 is electroformed for 25-40 minutes to form a projection 14.
Referring to FIG. 3, the conventional electroforming process utilizes direct current with a voltage of -4.5 volts. The current for the electroforming process is continuous and so the electroforming process will keep on until the power is turned off. Such an electroforming process is fast and fit for forming an object with large area or volume such as oscillating plate, but unsuitable for forming smaller object such as the projection.
Referring to FIG. 4, since the conventional electroforming process utilizes continuous direct current, it is very difficult to control the shape of the projection 14 and an excessive electroforming portion 141 will be formed on the projection 14. The excessive electroforming portion 141 will influence the resolution of the print head and so it is preferable to have a projection 14 with sharp edges. In other words, the removal of the excessive electroforming portion 141 will be helpful for the space arrangement design of the actuator and facilitate the alignment between the actuator and the projection.
The ink-jet printers with low resolution does not have a compact structure and so the existance of the excessive electroforming portion 141 is acceptable. However, the execessive portion 141 will limit the space arrangement design of the actuator and influence the accuracy in aligning the actuator with the projection, thereby causing a problem in manufacture and seriously influence the product quality.
Therefore, it is an object of the present invention to provide a method of controlling excessive electroforming portion on the projection of the oscillating plate, which can obviate and mitigate the above-mentioned drawbacks.